Ignition distributor with improved cam timing means

ABSTRACT

Three sets of breaker points are used in an ignition distributor, two of which are in parallel with each other and the third of which is in series. The parallel pair is operated so that the dwell of the two sets overlap while the third set of points has a dwell time between successive operations of the parallel pair. The time of operation of the third set of points may be chosen to produce an irregular pattern of ignition sparks.

O United States Patent 1111 3,575,5

[72] Inventor Rogerlhbert [56] RefereneesCited IN :1 3:16 UNITED STATES PATENTS [21] App. 0. [22] PM lunmm 2,559,341 1/1951 Flubacker ..2o0/1s5 .13)x A 2o 2,579,928 12/1951 ,Kangas 200/21 i 2,780,488 2/1957 Kennedy 74/567X 73 Asslgnee 311:; F et 19 2,821,580 1/1958 Black 200/1l(D)X 'fig 3,189,695 /1965 Randolph.. zoo/11 1) Pmmy 3,189,696 6/1965 Nuttall zoo/11 1) 511 155438 Primary Examiner-J. R. Scott IGNITION DISTRIBUTOR WITII IMPROVED CAM TIMING MEANS 32, 153.11, 153.12, 153.13, 153.19, 6 (B1), 33.2, 37.1, 38 (B), 38 (B1), 38 (C), 38 (Cl), 11 (D); 74/568 Attorney-Imirie and Smiley ABSTRACT: Three sets of breaker points are used in an 7 ignition distributor, two of which are in parallel with each PATENTEUAPRZO :sm

WVENTOR ROGER HABERT ATTORNEYS IGNITION DISTRIBUTOR WITH IMPROVED CAM TIMING MEANS BACKGROUND OF THE INVENTION The number of lobes in a distributor cam usually equals the number of cylinders serviced by the distributor. With multicylinder internal combustion engines, the dwell time of a single set of breaker points may be insufficient to produce the requisite voltage at the secondary of the ignition coil at higher rotational speeds of the engine. Dual breaker points have been proposed to obtain the requisite dwell time but in all such cases the intervals between successive ignition sparks are the same and, since certain engine configurations may require an irregular firing cycle, such prior solutions are inadequate unless resort is had to the use of two separate distributor assemblies.

BRIEF SUMMARY OF THE INVENTION The present invention is directed to an ignition distributor assembly which may provide an irregular firing cycle with adequate dwell time. Essentially, the present system employs three breaker point sets, two of which are connected in electrical parallel and the third of which is connected in series with the first two. The distributor cam has a plurality of lobes equal to half the number of cylinders serviced and the first two sets of breaker points are operated with overlap to open and close the primary circuit of the ignition coil to produce alternate ignition sparks. The third set of breaker points is operated subsequent to the operation of the first two to produce alternate ignition sparks. The time of opening the third set of points may be chosen to produce a desired irregular firing cycle pattern.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. I is a diagrammatic view illustrating an irregular firing cycle pattern;

FIG. 2 is a plan view of a portion of the distributor constructed in accordance with the present invention;

FIG. 3 is a circuit diagram of the breaker point sets;

FIG. 4 is a diagrammatic view illustrating the relative dispositions between the various breaker point sets and the distributor cam; and

FIG. 5 is time base diagram illustrating the operations of the distributor point sets.

DETAILED DESCRIPTION OF THE INVENTION The basic construction of a distributor in accord with the present invention may be seen in FIG. 2 wherein reference character 11 designates the conventional breaker plate and reference characters 2, 3, and 4 indicate in general the three sets of breaker points for producing an irregular firing cycle as is illustrated in FIG. 1.

A firing cycle such as is illustrated in FIG. 1 represents the firing cycle of a six cylinder engine which may be required in certain engine configurations. For example, a V-6 engine of small included angle between the banks of cylinders, i.e. other than 60 or 120, and operating with a crankshaft of conventional configuration may require the irregular firing cycle pattern depicted in FIG. 1.

As in conventional, the breaker points 2, 3 and 4 each embody a mounting bracket portion 5 by means of which they are removably secured to the breaker plate 1 and a conductor 6 is provided which extends to the ignition coil, completing, through the breaker point sets, the electrical circuit of the primary of the ignition coil. As is well known, when the primary circuit is opened causing the primary field to collapse, and ignition spark is induced in the coil secondary which, by means of a lead extending to the distributor cap and the requisite distributor rotor in conjunction with individual leads from the distributor cap to the spark plugs applies the ignition spark to the proper spark plug.

Each set of points also includes a rubbing block assembly 7 which operates to open and close the movable breaker point contact 8 with respect to the fixed contact point 11, each such breaker block portion 7 being provided with the respective tips 2a, 3a and 4a which are engaged by the individual lobes of the distributor cam 14 which is rotatably driven in the direction of the arrow shown in FIG. 2 in conventional fashion.

As is also conventional, the movable arm 9 of each breaker point set is pivotally mounted on a post 10 provided on the mounting plate 5 and electrical connection to the movable arms is made by means of the spring member 13 which also serves to maintain the rubbing block tips 2a, 3a and 4a in contact with the cam lobes when engaged thereby. The upstanding ears 18a and 18b on the mounting plate 5 respectively mount the fixed contact points 11 and the spring arms 13 and associated conductors 6 and 66. Additionally, provision is made at 12 for adjustment of the mounting plate 5 to vary the opening of the ignition points by allowing angular inward movement of the rubbing block tips 2a, 3a and 4a.

As is shown in FIG. 3, the two sets of points 2 and 3 are disposed in electrical parallel and are also disposed in series with the third set of points 4 and it will be appreciated that the cycle of operations is such that the set of points 2 first opens and, while still open, the second set of points 3 opens thereby to break the ignition coil primary circuit to produce a spark, whereafter the point set 2 will again close to reestablish the ignition coil primary circuit, whereafter the third set of points 4 will open to produce a second spark and will close before the next opening operation of the points 2 and 3.

This is illustrated in FIG. 4 wherein the cam lobe 14a operation in the direction of distributor cam rotation as indicated by the arrow F is just engaging at point 15 with the breaker point rubbing block tip 2a. At the same time, the cam lobe 14b is spaced from the rubbing block tip 3a by the angle 6 as illustrated and the rubbing block tip 4a is angularly spaced from the cam lobe 14c by the angle or, the points of contact between the respective cam lobes 14b and with respect to their rubbing block tips 3a and 4a being designated by the reference characters 16 and 17. It will further be noted that the angular disposition between the rubbing block points 3a and 4a equals the angle B and whereas the opening of the points 3 effects the ignition coil to produce the first spark with respect to the diagram of FIG. 4 whereas the third breaker point 4 operates to produce the second spark, the angular timing between these two sparks will be equal to B.

This is better illustrated in FIG. 5 wherein it will be seen that after the distributor cam 14 has rotated through the angle 9 in FIG. 4, during which time the point set 2 is open, the point set 3 will also be open and since the times t and t, representative of the dwell times of the points 2 and 3 overlap, the first shaded area in FIG. 5 represents the time during which the ignition coil primary circuit will be open to produce the first ignition spark. Subsequently, at the beginning time t the ignition points 4 will open to produce the second spark as indicated by the second shaded portion in FIG. 5. After the distributor cam 14 rotates through the angle B as indicated in FIG. 5, the next operation of the points 2 and 3 will be effected to produce a third spark, whereafter the breaker point set 4 produces the fourth spark and so on to produce the irregularly spaced firing cycle as depicted in FIG. 1. The angle a will be seen to be equal to a. minus 9 whereas the angle [3 will 'of course be the angular separation between the point rubbing block tips 3a and 4a.

Thus, according to the present invention, a number of cam lobes equal to half the number of cylinders serviced may be utilized thereby easily to provide the requisite dwell times due to the reduced number of lobes and the utilization of the three sets of points permits of a desired irregular pattern of ignition sparks to be provided.

lclaim:

1. In an ignition distributor for an internal combustion engine having a plurality n of cylinders, in combination,

a rotatable cam having n/2 lobes, and

successive pairs of said electrical impulses are separated by different times.

first, second and third switch means for producing a succession of 1: electrical impulses per revolution of said cam, said first and second switch means being disposed in electrical parallel with each other and in series with said third switch means, said first and second switch means 5 being operated sequentially with overlap and said third switch means being operated subsequent to operation of said first and second switch means.

2. In an ignition distributor as defined in claim 1, wherein 3. In an ignition distributor for multicylinder internal combustion engines, in combination,

a rotatable cam having a' plurality of lobes, and

first, second and third normally closed breaker point assemblies circumferentially spaced around said cam for sequential actuation thereby,

said first and second breaker point assemblies being disposed in electrical parallel and both being disposed in electrical series with said third breaker point assembly, said breaker point assemblies having respective rubbing blocks in which the rubbing blocks of said first and second breaker point assemblies are disposed for sequential engagement by said cam, with overlap, so that a first ignition spark is produced when said second breaker point assembly is opened, and the rubbing block of said third breaker point assembly being disposed for engagement by said cam subsequent to opening and then closing of said second breaker point assembly, so as to produce a second ignition spark prior to the next actuation of said first and second breaker point assemblies to produce a third ignition spark.

4. ln an ignition distributor as defined in claim 3, wherein the angular timing between said first and second ignition sparks is different from the angular timing between said second and third ignition sparks. 

1. In an ignition distributor for an internal combustion engine having a plurality n of cylinders, in combination, a rotatable cam having n/2 lobes, and first, second and third switch means for producing a succession of n electrical impulses per revolution of said cam, said first and second switch means being disposed in electrical parallel with each other and in series with said third switch means, said first and second switch means being operated sequentially with overlap and said third switch means being operated subsequent to operation of said first and second switch means.
 2. In an ignition distributor as defined in claim 1, wherein successive pairs of said electrical impulses are separated by different times.
 3. In an ignition distributor for multicylinder internal combustion engines, in combination, a rotatable cam having a plurality of lobes, and first, second and third normally closed breaker point assemblies circumferentially spaced around said cam for sequential actuation thereby, said first and second breaker point assemblies being disposed in electrical parallel and both being disposed in electrical series with said third breaker point assembly, said breaker point assemblies having respective rubbing blocks in which the rubbing blocks of said first and second breaker point assemblies are disposed for sequential engagement by said cam, with overlap, so that a first ignition spark is produced when said second breaker point assembly is opened, and the rubbing block of said third breaker point assembly being disposed for engagement by said cam subsequent to opening and then closing of said second breaker point assembly, so as to produce a second ignition spark prior to the next actuation of said first and second breaker point assemblies to produce a third ignition spark.
 4. In an ignition distributor as defined in claim 3, wherein the angular timing between said first and second ignition sparks is different from the angular timing between said second and third ignition sparks. 